Revert "Merge pull request #9902 from NixOS/require-fixed-output-fetc…

…hurl"

This is not actually a bug on Nix (version 2.18, at least), and breaks code
I've written (with no other way to write that code.)

    nix-repl> :b builtins.derivation { name = "nix-cache-info"; system = "x86_64-linux"; builder = "builtin:fetchurl"; url = https://cache.nixos.org/nix-cache-info; outputHashMode = "flat"; }
    warning: error: unable to download 'https://cache.nixos.org/nix-cache-info': Couldn't resolve host name (6); retrying in 309 ms
    warning: error: unable to download 'https://cache.nixos.org/nix-cache-info': Couldn't resolve host name (6); retrying in 607 ms
    warning: error: unable to download 'https://cache.nixos.org/nix-cache-info': Couldn't resolve host name (6); retrying in 1002 ms
    warning: error: unable to download 'https://cache.nixos.org/nix-cache-info': Couldn't resolve host name (6); retrying in 2554 ms
    error: builder for '/nix/store/z89j6fdfm6k9k1qir99449wyvldpm2ma-nix-cache-info.drv' failed with exit code 1;
           last 4 log lines:
           > error:
           >        … writing file '/nix/store/l9ax62fdagg4cvw9wd4h84cf4pxqcmlg-nix-cache-info'
           >
           >        error: unable to download 'https://cache.nixos.org/nix-cache-info': Couldn't resolve host name (6)
           For full logs, run 'nix-store -l /nix/store/z89j6fdfm6k9k1qir99449wyvldpm2ma-nix-cache-info.drv'.

This reverts commit 081dc5d, reversing
changes made to ef6d055.

src/libstore/builtins/fetchurl.cc

@@ -16,14 +16,6 @@ void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData)
         writeFile(settings.netrcFile, netrcData, 0600);
     }
 
-    auto out = get(drv.outputs, "out");
-    if (!out)
-        throw Error("'builtin:fetchurl' requires an 'out' output");
-
-    auto dof = std::get_if<DerivationOutput::CAFixed>(&out->raw);
-    if (!dof)
-        throw Error("'builtin:fetchurl' must be a fixed-output derivation");
-
     auto getAttr = [&](const std::string & name) {
         auto i = drv.env.find(name);
         if (i == drv.env.end()) throw Error("attribute '%s' missing", name);
@@ -67,11 +59,13 @@ void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData)
     };
 
     /* Try the hashed mirrors first. */
-    if (dof->ca.method.getFileIngestionMethod() == FileIngestionMethod::Flat)
+    if (getAttr("outputHashMode") == "flat")
         for (auto hashedMirror : settings.hashedMirrors.get())
             try {
                 if (!hasSuffix(hashedMirror, "/")) hashedMirror += '/';
-                fetch(hashedMirror + printHashAlgo(dof->ca.hash.algo) + "/" + dof->ca.hash.to_string(HashFormat::Base16, false));
+                std::optional<HashAlgorithm> ht = parseHashAlgoOpt(getAttr("outputHashAlgo"));
+                Hash h = newHashAllowEmpty(getAttr("outputHash"), ht);
+                fetch(hashedMirror + printHashAlgo(h.algo) + "/" + h.to_string(HashFormat::Base16, false));
                 return;
             } catch (Error & e) {
                 debug(e.what());

tests/functional/fetchurl.sh

@@ -78,9 +78,3 @@ outPath=$(nix-build -vvvvv --expr 'import <nix/fetchurl.nix>' --argstr url file:
 
 test -x $outPath/fetchurl.sh
 test -L $outPath/symlink
-
-# Make sure that *not* passing a outputHash fails.
-requireDaemonNewerThan "2.20"
-expected=100
-if [[ -v NIX_DAEMON_PACKAGE ]]; then expected=1; fi # work around the daemon not returning a 100 status correctly
-expectStderr $expected nix-build --expr '{ url }: builtins.derivation { name = "nix-cache-info"; system = "x86_64-linux"; builder = "builtin:fetchurl"; inherit url; outputHashMode = "flat"; }' --argstr url file://$narxz 2>&1 | grep 'must be a fixed-output derivation'